Process for cleaning objects



2,901,383 Patented Aug. 25, 1959 2,901,383 PROCESS FOR CLEANING OBJECTS Kurt Lebsanft, Munich-Lochham, and. Ernst Schmidt,

Munich, Germany, assignors to Wacker-Chemie G.m.b.H., Munich, Germany, a corporation of Germany No Drawing. Application October 1, 1956 Serial No. 612,971

This invention relates to cleaning objects by means of chlorinated aliphatic hydrocarbons, particularly trichlorethylene and perchlorethylene, and it has for its object to provide a novel and improved process for this purpose.

Another object of the invention is to expedite, and materially reduce the cost, of removing insoluble impurities from objects treated by cleaning processes of the type specified.

Still another object is to provide a novel, efficient and economical cleaning composition for the above purpose.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

This application is a continuation-impart of application Serial No. 251,823, filed October 17, 1951, and now abandoned.

It is a well known practice to clean all sorts of objects with chlorinated aliphatic hydrocarbons such as trichlorethylene, perchlorethylene and the like. To cite just one example, brass plates which have been lying around a factory or Warehouse, and have become encrusted with grease, dust and dirt, must be thoroughly cleaned before they can be fabricated into bright, shiny radio panels, etc., and the above-mentioned cleaning fluids have frequently been used for such purpose.

In cleaning such objects, as well as many others, it is also a well known practice to mix finely distributed in soluble solids with the liquid chlorinated hydrocarbon in order to increase the cleaning elfect. In this way it is possible to remove from the objects to be cleaned, not only soluble impurities such as oils, fats and the like, but also insoluble impurities such as bearing dust, grinding media and the like. Heretofore sawdust, asbestos fibers, bits of leather, textile fibers and the like, which are insoluble in the chlorinated hydrocarbon, have been used for this purpose.

However, there is a serious drawback in the above-mentioned practice in that, after the cleaning operation and the evaporation of the solvent, many of the finely divided solid substances remain stuck to the cleaned articles and they cannot be removed even in a subsequent rinsing bath. Consequently, the adhering solid substances must be freed from the cleaned articles by costly hand labor.

We have now discovered that the foregoing disadvantages of prior art processes can be entirely eliminated by mixing with the chlorinated aliphatic hydrocarbon cleaning liquid, preferably trichlorethylene or perchlorethylene, finely distributed solids consisting of polyvinyl chloride, especially ball-shaped polyvinyl chloride particles with a diameter of 0.5-1 mm., and, after the cleaning operation, preferably treating the cleaned objects in a rinsing bath which may be the same kind of liquid as that employed for the cleaning bath.

During the cleaning operation the polyvinyl chloride particles may be kept in motion by mechanically stirring the liquid cleaning solvent, particularly when the solvent is not boiling; but if the solvent is boiling a mechanical motion is not necessary since the polyvinyl chloride par- 2 ticles are kept in constant distribution in the liquid by the bubbles of vapor. t 1

Example I The cleaning fluid consists of liquid trichlorethylene contained in a vat or tank of .any suitable dimensions which may be heated in any convenient manner since in some cases, depending upon the objects to be cleaned, it may be desirable to maintain the bath at an elevated or boiling temperature. Into the liquid trichlorethylene there are dumped about 5% by weight of ball-shaped particles of polyvinyl chloride (mean molecular weight 47,000) of 0.5-1 mm. diameter. If the temperature of the trichloroethylene is 35 C. or less, the particles of polyvinyl chloride will float on the liquid, hence at such temperatures the bath is preferably kept in motion by any suitable mechanical means to elfect a distribution of the particles in the bath. When the temperature is raised above 35 C. the heating and boiling of the liquid agitates the liquid and effects a distribution of the polyvinyl chloride particles.

The objects to be cleaned, for example greaseand dirtencrusted metal plates of the type previously mentioned, are lowered into, and submerged in, the cleaning bath. Not only the motion of the liquid referred to above, but also the descending motion of the submerging objects or plates themselves, and their subsequent ascending motion, causes the particles of polyvinyl chloride to positively wipe and rub against thesurfaces of said objects. The combined action of the trichlorethylene and the particles of polyvinyl chloride quickly removes all soluble impurities as well as insoluble impurities from the submerged objects. Any particles of polyvinyl chloride adhering to the cleaned objects after withdrawing the latter from the trichlorethylene are quickly removed by simply dipping such objects in a rinsing bath consisting of a liquid chlorinated hydrocarbon, for example liquid trichlorethylene.

Example II The process described in Example 1 is repeated with only one difference, namely, the cleaning fluid consists of liquid perchlorethylene. The ball-shaped particles of polyvinyl chloride ordinarily float on perchlorethylene at any temperature. However, the particles are uniformly distributed in the liquid perchlorethylene either by any suitable mechanical motion or stirring, or by heating the liquid to a temperature of C. or higher, particularly during boiling. In actual practice, furthermore, an effective distribution of the polyvinyl chloride balls in the solvent takes place positively by simply dipping (submerging) the objects to be cleaned into, and removing same from, the solvent. As a result the polyvinyl chloride balls are always distributed in the solvent, whether the solvent boils or not.

After the cleaned objects have been removed from the cleaning bath, any adhering particles of polyvinyl chloride are easily and quickly removed by dipping said objects in a rising bath consisting of a liquid chlorinated hydrocarbon, for example perchlorethylene.

Although certain specific embodiments of the invention are set forth herein for purposes of illustration, it will be evident to those skilled in the art that the invention is capable of various modifications and adaptations within the scope of the appended claims.

The invention claimed is:

1. Process for cleaning objects which comprises immersing them in and removing them from a substance selected from the group consisting of trichlorethylene and perchlorethylene and containing about 5% by weight of finely divided ball-shaped particles of polyvinyl chloride of molecular weight 47,000.

2. Process for cleaning objects which comprises immersing them in and, removing, them from. a substance 1 selected from the group consisting of trichlorethylene and perchlorethyl'ene and containing finely distributed ballshaped particles of polyvinyl chloride of 0.5-1 mm. di-

ameter.-

3. Process for cleaning objects which comprises irnmersing them in and removing them from a substance selected from the group consisting of trichlorethylene and perchlorethylene and containing about 5% by weight of ball shapedarticles of polyvinyl chloride of 05-15mm. diameter.

4. Process for cleaningobjects which comprises immer sing them. 'in and removing them from a chlorinated aliphatic hydrocarbon selected from the group; consisting of trichlorethylene a-nd perchlorethylene and containing about 5% by weightof finely distributed ball-shaped particles of polyvinyl chloride of 0.5-1 mm. diameter and means molecular weight 47,000, and'then rinsing the cleaned objects in a chlorinated hydrocarbon selected from the aforesaid group to remove the polyvinyl chloride particles. V

5. Process for cleaning objects which comprises imniersing them in and removing them from a chlorinated aliphatic hydrocarbon selected from the group consisting 4: 8. Process for cleaning objects/which comprises treating them with a chlorinated aliphatic hydrocarbon containing finely divided particles of polyvinyl chloride, and

of trichlorethylene and perchlorethylene and containing about 5% by weight of finely distributed ball-shaped particles of polyvinyl chloride of 0.5-.1 mm. diameter and mean molecular weight 47,000.

6. Process for cleaning objects which comprises treating them with a chlorinated aliphatic hydrocarbon containing finely divided particles of polyvinyl chloride.

7. Process for cleaning objects which comprises treating them with a chlorinated aliphatic hydrocarbon containing, finely divided ball-shaped particles of polyvinyl chloride. 7 i V r subsequently rinsing the cleaned objects in a chlorinated aliphatic hydrocarbon to remove the polyvinyl chloride particles. A

9. Process for cleaning objects which comprises treating them with a chlorinatedaliphatic hydrocarbon containing finely. distributed ball-shaped particles of poly. vinyl chloride of 0.5-1 mm. diameter, and then rinsing the cleaned objects, in a chlorinated aliphatic hydrocarbon to remove the polyvinyl chloride particles.

10. Process for cleaning objects which comprises treating them with a chlorinated hydrocarbon selected from the group consisting of trichlorethylene and perchlorethylene containing finely distributed ball-shaped particles of polyvinyl chloride of 0.5-1 mm. diameter, and then rinsing the cleaned objects in a chlorinated hydrocarbon selected from the aforesaid group to remove the polyvinyl chloride particles. t 1

References Cited in the file of this patent UNITED STATES PATENTS 2,517,356 Sale Aug. 1, 19.50 2,525,303 Lenoble Oct. 10, 1950, 2,627,148 McDougal et al Feb. 3, 19.53

V FOREIGN PATENTS 965,236 France Feb. 14,1950

OTHER REFERENCES 1 Soc. Chem. Ind., Transaction, 56, 363T-375T (Coltof, W. 1.), 1937. 

8. PROCESS FOR CLEANING OBJECTS WHICH COMPRISES TREATING THEM WITH A CHLORINATED ALIPHATIC HYDROCARBON CONTAINING FINELY DIVIDED PARTICLES OF POLYVINYL CHLORIDE, AND SUBSENQUENTLY RINSING THE CLEANED OBJECTS IN A CHLORINATED ALIPHATIC HYDROCARBON TO REMOVE THE POLYVINYL CHLORIDE PARTICLES. 